Effect of Strain Rate and Temperature on the Tensile Properties of Long Glass Fiber-Reinforced Polypropylene Composites

Strain rate and temperature are influential factors that significantly impact the mechanical properties of long glass fiber-reinforced polypropylene composites. This study aims to investigate the tensile properties of these composites, analyzing the effects of temperature, strain rate, and their interplay on variables such as tensile stress, tensile strength, fracture stress, and fracture morphology through a series of comprehensive tensile experiments. The experimental results demonstrate a notable increase in both tensile strength and tensile fracture stress when the temperature is set at 25 °C, accompanied by strain rates of 10(−4), 10(−3), 10(−2), and 10(−1) s(−1). Conversely, a significant decrease is observed in the aforementioned properties when the strain rate is fixed at 10(−4), while varying temperatures of −25 °C, 0 °C, 25 °C, 50 °C, and 75 °C are applied. At lower temperatures, cracks manifest on the fracture surface, while matrix softening occurs at higher temperatures. Additionally, in the context of strain rate–temperature coupling, the decreasing trend of both tensile strength and tensile fracture stress decelerates as the temperature ranges from −25 °C to 75 °C at a strain rate of 10(−1), compared to 10(−4) s(−1). These findings highlight the significant influence of both strain rate and temperature on high fiber content long glass fiber-reinforced polypropylene composites.